Abstract
Cobalt ferrite is synthesized via a simple solvothermal method. Then, the effect of the degree of cobalt-ferrite growth on its morphology, structure, electromagnetic performance, and microwave absorption is studied as a function of the solvothermal reaction time. When the reaction time during synthesis is 8 h, the structure of cobalt ferrite is hollow spheres. In addition, when the reaction time is 12 h and 16 h, it becomes a submicron sphere with a diameter of 100–150 nm. With the increase of reaction time, cobalt ferrite underwent the process of cobalt ferrite formation, hollow structure formation, hollow structure disappearance, agglomeration separation and reagglomeration in 4–16 h. In general, CoFe2O4-8h shows better microwave absorption-the effective absorption bandwidth is 9.84 GHz (6–15.84 GHz) for a thickness of 1.72–3.72 mm. This represents a minimum return loss of −47.24 dB. A better understanding of both the synthesis parameters and the relationship between structure and electromagnetic properties can open new possibilities for applications and the development of microwave absorbing materials.
Highlights
Ferrites are ferromagnetic metal-oxides with both magnetic and electric absorption capabilities [1,2].Because of its stable chemical properties, strong high-frequency permeability, wide frequency-band and strong absorption, ferrites are often used as microwave absorbers [3,4,5]
When the reaction time increased, the diffraction pattern did not change much, which indicates that the increase of the reaction time has little effect on the phase and crystallinity of cobalt ferrite
The synthesis of cobalt ferrite hollow spheres is related to the gas-assisted maturation mechanism of Ostwald
Summary
Ferrites are ferromagnetic metal-oxides with both magnetic and electric absorption capabilities [1,2]. Because of its stable chemical properties, strong high-frequency permeability, wide frequency-band and strong absorption, ferrites are often used as microwave absorbers [3,4,5] Based on their crystal structure, ferrite materials are mainly spinel-type, magnetoplumbite-type, and garnet-type [6]. In particular, is one of the most widely studied spinel-type ferrites due to its high saturation magnetization and high-frequency permeability, high Snoek-limit, excellent chemical stability, high mechanical hardness, high cubic magneto-crystalline anisotropy, and low cost [7,8,9]. It is widely used as an electromagnetic absorber. This study has some guiding significance for the synthesis of cobalt ferrite and cobalt ferrite composite absorbing materials
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